title: Simultaneous quantification of anidulafungin and caspofungin in plasma by an accurate and simple liquid chromatography tandem mass-spectrometric method.
abstract: BACKGROUND
  Echinocandins are a valuable addition for the treatment of invasive fungal infections, as they are efficacious, demonstrate low toxicity, and have limited drug-drug interactions. In specific clinical situations when altered pharmacokinetics can be expected or dosing guidelines are conflicting, it may be useful to measure concentrations. For this purpose, a liquid chromatography tandem mass-spectrometric method to measure anidulafungin and caspofungin in ethylenediaminetetraacetic acid plasma was developed.
  
  
  METHODS
  The method was developed on a Thermo Fisher TSQ Quantum LC-MS/MS. For separation, a BetaBasic C4 (100 mm × 3.0 mm; 5 μm) analytical column was used. Sample preparation consisted of protein precipitation directly in the autosampler vial. The internal standard aculeacin A is structurally related, not used in humans, and commercially available. The method was validated according to the guidelines for bioanalytical method validation of the Food and Drug Administration.
  
  
  RESULTS
  The method was accurate (bias ranging from -3.0% to 1.9%) and precise (within-run and between-run coefficients of variation of 2.2% to 7.7% and 1.6% to 9.0%, respectively). All calibration curves were linear over a range of 0.5-10.0 mg/L for anidulafungin and 0.1-20.0 mg/L for caspofungin, and if necessary, samples can be diluted 10-fold. The samples were stable for 3 freeze-thaw cycles, with a bias ranging from 0.6% to 11%. The maximum bias from the worst storage condition, 72 hours at room temperature, was -14.7%. In patient samples, anidulafungin peak concentrations ranged from 2.8 to 8.6 mg/L (n = 20) and trough concentrations ranged from 1.0 to 4.7 mg/L (n = 79). The measured caspofungin concentrations ranged from 1.9 to 7.3 mg/L (n = 20).
  
  
  CONCLUSIONS
  The method developed has a straightforward sample preparation and uses a structural analog as the internal standard. This method has been applied successfully for the measurement of anidulafungin and caspofungin concentrations in patient samples, both for clinical practice and for research.
authors.affiliation: Department of Clinical and Hospital Pharmacy, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Dr Santoe is now with the Helpman Pharmacy, 9721 CX Groningen, The Netherlands. Dr Wilmer is now with the Department of Clinical Pharmacy, Radboud University Nijmegen Medical Centre, 6525 GA Nijmegen, The Netherlands.
authors.forename: Marjolijn J P
authors.initials: MJ
authors.lastname: van Wanrooy
authors.forename: Riaaz N
authors.initials: RN
authors.lastname: Santoe
authors.forename: Kim C M
authors.initials: KC
authors.lastname: van der Elst
authors.forename: Carli M
authors.initials: CM
authors.lastname: Wilmer
authors.forename: Kai
authors.initials: K
authors.lastname: van Hateren
authors.forename: A Mireille A
authors.initials: AM
authors.lastname: Wessels
authors.forename: Ben
authors.initials: B
authors.lastname: Greijdanus
authors.forename: Jan-Willem C
authors.initials: JW
authors.lastname: Alffenaar
authors.forename: Donald R A
authors.initials: DR
authors.lastname: Uges
mesh_terms: D000328:Adult; D000077612:Anidulafungin; D000935:Antifungal Agents / Q000097:blood; D002138:Calibration; D000077336:Caspofungin; D002648:Child; D002675:Child, Preschool; D002853:Chromatography, Liquid / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods; D004355:Drug Stability; D004356:Drug Storage; D054714:Echinocandins / Q000097:blood*; D006801:Humans; D007223:Infant; D055666:Lipopeptides; D008297:Male; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D000077612:Anidulafungin; D000077336:Caspofungin